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c7821c2d9c
When a protocol registers its events, the notification core takes care
to rescan the hashtable of pending event handlers and activate all the
possibly existent handlers referring to any of the events that are just
registered by the new protocol. When a pending handler becomes active
the core requests and enables the corresponding events in the SCMI
firmware.
If, for whatever reason, the enable fails, such invalid event handler
must be finally removed and freed. Let us ensure to use the
scmi_put_active_handler() helper which handles properly the needed
additional locking.
Failing to properly acquire all the needed mutexes exposes a race that
leads to the following splat being observed:
WARNING: CPU: 0 PID: 388 at lib/refcount.c:28 refcount_warn_saturate+0xf8/0x148
Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development
Platform, BIOS EDK II Jun 30 2020
pstate: 40000005 (nZcv daif -PAN -UAO BTYPE=--)
pc : refcount_warn_saturate+0xf8/0x148
lr : refcount_warn_saturate+0xf8/0x148
Call trace:
refcount_warn_saturate+0xf8/0x148
scmi_put_handler_unlocked.isra.10+0x204/0x208
scmi_put_handler+0x50/0xa0
scmi_unregister_notifier+0x1bc/0x240
scmi_notify_tester_remove+0x4c/0x68 [dummy_scmi_consumer]
scmi_dev_remove+0x54/0x68
device_release_driver_internal+0x114/0x1e8
driver_detach+0x58/0xe8
bus_remove_driver+0x88/0xe0
driver_unregister+0x38/0x68
scmi_driver_unregister+0x1c/0x28
scmi_drv_exit+0x1c/0xae0 [dummy_scmi_consumer]
__arm64_sys_delete_module+0x1a4/0x268
el0_svc_common.constprop.3+0x94/0x178
do_el0_svc+0x2c/0x98
el0_sync_handler+0x148/0x1a8
el0_sync+0x158/0x180
Link: https://lore.kernel.org/r/20201013133109.49821-1-cristian.marussi@arm.com
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.